Factory farms tend to monitor and cull livestock as needed to try to prevent this.

Meat markets like the one where this pandemic is believed to have started? Not so much.

When we're through this thing, there darn well better be treaties on the table that require the reduction and elimination of trade in untested disease-carrying animals.

The point is that there are multiple vectors. A new pathogenic strain of SARS or H1N1 may not be caught in a factory farm either because it isn't detected early enough.